Flexible protective coating

ABSTRACT

A composition made up of an inorganic fire-retardant having at least a bimodal distribution of particle sizes.

FIELD OF INVENTION

The invention relates generally to fire-retardant, smoke-suppressingcompositions. More particularly the invention relates to fire-retardant,smoke-suppressing compositions that can be applied to a substrate.

BACKGROUND OF THE INVENTION

Numerous approaches have been developed to protect flammable substratesfrom fire. One approach that has found widespread utility is theapplication of fire-retardant coatings to the substrate. Fire-protectivecoatings may be broadly classified as ceramic-based coatings, ablativecoatings, intumescent coatings, and vapor-producing (sublimation)coatings, although in practice there may be substantial overlap of thechemical and physical fire-retarding mechanism between these approaches.

Many conventional fire-retardant coatings employ agents which releasenon-flammable gases in response to heat or flame. For example,halogenated fire-retardants release gaseous acids, such as hydrobromicor hydrochloric acid, which retard burning by scavenging oxygenradicals. However, environmental and health concerns over halogenatedflame retardant chemicals, such as brominated organic polymers, has ledto an renewed emphasis on inorganic flame-retardants.

Alumina trihydrate (“ATH”) is an inorganic flame retardant defined bythe chemical formula Al₂O₃.3H₂O. In the presence of heat from fire, ATHendothermically releases its water of hydration which comprises 35% ofthe molecular weight of ATH. The endothermic reaction helps to cool thesubstrate below its flash point. The liberated water also provides avapor barrier which shields the substrate from oxygen needed forcombustion.

There are certain drawbacks to conventional coatings containing ATH andother inorganic fire-retardants. For example, due to the high levels ofinorganic fire-retardant required to impart acceptable fire-retardancy,the coatings are typically rigid and therefore not suitable forapplication to highly flexible substrates. Cracking and checking of thecoating frequently results when the underlying substrate is deformed,thereby diminishing the protective ability of the coating, exposing thesubstrate to the elements, and detracting from the visual appearance ofthe article.

Accordingly, there is a need in the art for highly flexiblefire-retardant coatings. Further, there is a need in the art for highlyflexible fire-retardant coatings comprising inorganic fire-retardants inquantities sufficient to retard or resist combustion of a substrate.There is also a need in the art for highly flexible fire-retardantcoatings comprising inorganic fire-retardants in quantities sufficientto retard or resist combustion of a substrate which further protect thesubstrate or under-coating from water damage and the like.

SUMMARY OF THE INVENTION

In accordance with the foregoing objectives and others, the presentinvention overcomes the deficiencies in conventional fire-retardantcoatings by providing fire-retardant, smoke-suppressing coatingscomprising inorganic fire-retardants which are ideally suited forapplication to flexible substrates such as pipes, tubing, cabling andthe like. Coatings using variants of the claimed compositions do notcrack or check when the substrate is deformed, for example, by bending.Some variant coatings have excellent adhesive properties and can beapplied directly to a substrate, including for example, metal, plastic,and wood, or may be applied over one or more under-coatings. Somevariant coatings are water-resistant and therefore protect the substrateor under-coating against the elements and prevent leaching of theinorganic fire-retardants from the coating.

Some variants of the compositions claimed herein involve (a) betweenabout 5% and about 30% by weight of an aqueous dispersion of polymericbinder; (b) between about 30% and about 90% by weight of awater-dispersible inorganic fire-retardant having a median particlediameter between about 15 and about 100 microns; and (c) between about0.1% and about 10% by weight of a surfactant.

Other variants of the compositions claimed herein involve an inorganicfire-retardant having at least a bimodal distribution of particle sizescomprising a first powder of inorganic fire-retardant having firstmedian particle diameter and a second powder of inorganic fire-retardanthaving a second median particle diameter; wherein the second medianparticle diameter is larger than the first median particle diameter.

Still other variant compositions claimed herein involve an inorganicfire-retardant, the inorganic fire-retardant having at least a bimodaldistribution of particle sizes comprising a first powder of inorganicfire-retardant having first median particle diameter between about 0.1and about 20 microns and a second powder of inorganic fire-retardanthaving a second median particle diameter between about 5 and about 100microns; with the proviso that the second median particle diameter islarger than the first median particle diameter; and wherein the weightratio of the first powder to the second powder is about 100:1 to about1:20. It should be understood that in such variants, the first andsecond inorganic fire-retardant powders are not necessarily the samecompound, although, in some, they will be the same. Some sub-variants ofthese compositions can comprise at least about 30% by weight inorganicfire-retardant.

Some exemplary variants of either of the above compositions willcomprise at least about 60% by weight, at least about 70% by weight, atleast about 80% by weight, or at least about 90% by weight inorganicfire-retardant.

The polymeric binder imparts flexibility to the above-referenced variantcoatings even at very high levels of inorganic fire-retardant.

Particular variants of the inorganic fire-retardant may involve, forexample, an inorganic oxide having water of hydration, such as aluminatrihydrate, hydrated magnesium oxide, and hydrated zinc borate.

Yet other variants claimed herein involve a fire-retardant coatingcomposition involving (a) alumina trihydrate having at least a bimodaldistribution of particle sizes comprising a first alumina trihydratepowder having a median particle diameter between about 0.1 and about 5microns and a second alumina trihydrate powder having a median particlediameter between about 20 and about 100 microns; wherein the weightratio of the first powder to the second powder is about 5:1 to about1:5; and (b) an aqueous dispersion of a latex binder; wherein thealumina trihydrate comprises at least about 30% by weight of thecomposition.

These and other aspects of the present invention will become apparent tothose skilled in the art after reading the following detaileddescription.

The advantages and features described herein are a few of the manyadvantages and features available from representative examples andvariants and are presented only to assist in understanding theinvention. It should be understood that they are not to be consideredlimitations on the invention as defined by the claims, or limitations onequivalents to the claims. For instance, some of these advantages aremutually contradictory, in that they cannot be simultaneously present ina single embodiment. Similarly, some advantages are applicable to oneaspect of the invention, and inapplicable to others. In addition,different permutations and combinations beyond those expressly set forthshould be understood to exist and can be created based upon thedescription provided herein without exhaustive recitation. Thus, thissummary of features and advantages should not be considered dispositivein determining equivalence. Additional features and advantages of theinvention will become apparent in the following description and from theclaims.

DETAILED DESCRIPTION

The present invention provides coatings in the form of water-basedcompositions comprising an inorganic fire-retardant and a polymericbinder which in various embodiments are fire-retardant, fire-resistant,and fire-extinguishing. The coatings are water-resistant and highlyflexible. In contrast to conventional coatings, the inventive coatingsare resistant to cracking and checking when the substrate to which theyare applied is deformed, such as by example bending or stretching. Thecoatings of the invention are also water-resistant which further servesto protect a substrate or undercoating from water damage and helpspreserve the efficacy of the inorganic fire-retardant in the coating.

As used herein, all terms are intended to have their ordinary meaning inthe art unless explicitly defined. The term “fire-retardant” refers tothe ability of a material to retard the progression of combustion onceignited. The term “fire-resistant” refers to the ability of a materialto resist combustion in the presence of heat of flame. The term“fire-extinguishing” refers to the ability of a material toself-extinguish upon combustion. The term “bimodal” refers to a particlesize distribution having two maxima. The term “trimodal” refers to aparticle size distribution having three maxima. All percentages andratios are provided on a weight basis unless otherwise specified herein.

The compositions of the invention comprise a polymeric binder. In thebroadest aspect of the invention, it is contemplated that any polymericbinder may be employed, including thermoplastic and thermosettingpolymers. In one embodiment, the polymeric binder is a water-dispersiblepolymer, including but not limited to latex binders. The polymericbinder may be provided, for example, as an aqueous colloidal dispersionof polymer particles having particles diameters between about 0.01microns and about 10 microns. Within this range, polymer particleshaving average particle diameters between about 0.05 microns and about 1micron are especially suitable.

With regard to the aforementioned latex binders, the skilled artisanwill recognize that the term “latex” is used in its broadest sense torefer to a colloidal suspension of polymeric particles and embraceswithout limitation natural latex, neoprene latex, nitrile latex, acryliclatex, vinyl acrylic latex, styrene acrylic latex, styrene butadienelatex, and the like. Exemplary polymers for these latex compositionsinclude, but are not limited to, methyl methacrylate, styrene,methacrylic acid 2-hydroxyethyl acrylate polymer (CAS # 70677-00-8),acrylic acid, methyl methacrylate, styrene, hydroxyethyl acrylate, butylacrylate polymer (CAS # 7732-38-6), butyl acrylate, methyl methacrylate,hydroxyethyl acrylate polymer (CAS # 25951-38-6), butyl acrylate,2-ethylhexyl acrylate, methyl methacrylate, acrylic acid polymer (CAS #42398-14-1), styrene, butylacrylate polymer (CAS # 25767-47-9), butylacrylate, 2-ethylhexyl acrylate, methacrylic acid polymer C (CAS #31071-53-1), acrylic polymers, and carboxylated styrene butadienepolymers. Combinations of more than one latex binder are alsocontemplated to be useful in the practice of the invention.

Special mention may be made of acrylic latex binders, such as those soldby The Dow Chemical Company under the name UCAR™ Latex. Suitable acryliclatex binders include, but are not limited to, UCAR™ Latex 120 (anacrylic latex binder material comprising about 48% by weight of anacrylic polymer, 52% by weight water, and 0.14% by weight ammonia,having has a total solids content of 50% by weight, viscosity of about200 cps, a bimodal particle size distribution, and a glass transitiontemperature, midpoint, of about −3° C.); UCAR™ Latex 9037 (an acryliccopolymer emulsion product comprising about 52% by weight butylacrylate, methyl methacrylate, hydroxyethyl acrylate polymer (CAS #25951-38-6), 48% by weight water, and 0.1% by weight ammonia, having atotal solids content of 51.5% by weight, viscosity of about 450 cps,average particle size of about 0.3 microns, and a glass transitiontemperature, midpoint, of about −30° C.); UCAR™ Latex 9042 (an acryliccopolymer emulsion product comprising about 54% by weight butylacrylate, methyl methacrylate, hydroxyethyl acrylate polymer (CAS #25951-38-6), 45% by weight water, and 0.12% by weight ammonia having atotal solids content of 55.5% by weight, viscosity of about 500 cps,average particle size of about 0.3 microns, and a glass transitiontemperature, midpoint, of about −35° C.); UCAR™ Latex 9043 (an acryliccopolymer emulsion product containing about 54% by weight butylacrylate, 2-ethylhexyl acrylate, methyl methacrylate, acrylic acidpolymer (CAS # 42398-14-1), 47% by weight water, 0.2% by weight ammonia,and 0.01% by weight 2-ethylhexylacrylate (CAS # 103-11-7) having a totalsolids content of 53% by weight, viscosity of about 175 cps, averageparticle size of about 0.3 microns, and a glass transition temperature,midpoint, of about −40° C.); UCAR™ Latex 9181 (an acrylic copolymeremulsion product comprising about 56% by weight butyl acrylate,2-ethylhexyl acrylate, methyl methacrylate, acrylic acid polymer (CAS #42398-14-1), 44% by weight water, 0.1% by weight ammonia, and 0.01% byweight 2-ethylhexylacrylate (CAS # 103-11-7) having a total solidscontent of 56.5% by weight, viscosity of about 450 cps, average particlesize of about 0.2 microns, and a glass transition temperature, midpoint,of about −40° C.); UCAR™ Latex 9188 (an acrylic copolymer emulsioncomprising about 58% by weight styrene, butylacrylate polymer (CAS #25767-47-9) and 42% by weight water and having a total solids content of57.3% by weight, viscosity of about 230 cps, average particle size ofabout 0.26 microns, and a glass transition temperature, midpoint, ofabout −29° C.); UCAR™ Latex 9189 (an acrylic copolymer emulsion productcontaining about 53% by weight butyl acrylate, methyl methacrylate,hydroxyethyl acrylate polymer (CAS # 25951-38-6), 47% by weight water,and 0.12% by weight ammonia having a total solids content of 52.5% byweight, viscosity of about 325 cps, average particle size of about 0.24microns, and a glass transition temperature, midpoint, of about −35°C.); UCAR™ Latex 9191 (an acrylic copolymer emulsion comprising about39% by weight butyl acrylate, methyl methacrylate, hydroxyethyl acrylatepolymer (CAS # 25951-38-6), 48% by weight water, 13% by weight of anaqueous dispersion of modified rosin (CAS # 8050-31-5), and 0.08% byweight ammonia and having a total solids content of 52.5% by weight,viscosity of about 250 cps, and a glass transition temperature,midpoint, of about −30° C.); UCAR™ Latex 9569 (an acrylic copolymeremulsion product containing about 58% by weight butyl acrylate,2-ethylhexyl acrylate, methacrylic acid polymer C (CAS # 31071-53-1),42% by weight water, 0.08% by weight 2-ethylhexyl acrylate (CAS #103-11-7), 0.06% by weight ammonia, and 0.01% by weight 1,4-dioxane andhaving a total solids content of 57.5% by weight, viscosity of about 900cps, average particle size of about 0.3 microns, and a glass transitiontemperature, midpoint, of about −53° C.).

Styrene acrylic latexes include, but are not limited to, UCAR™ Latex 100(a styrene acrylic latex comprising about 62% by weight butyl acrylate,methyl methacrylate, styrene, methacrylic acid 2-hydroxyethyl acrylatepolymer (CAS # 70677-00-8), 38% by weight water, and 0.04% by weightammonia and having a total solids content of 62% by weight, viscosity ofabout 750 cps, average particle size of about 0.3 microns, and a glasstransition temperature, midpoint, of about 12° C.) and UCAR™ Latex 462(a styrene acrylic latex binder comprising about 45.5% by weight acrylicacid, methyl methacrylate, styrene, hydroxyethyl acrylate, butylacrylate polymer (CAS # 7732-38-6) and about 54% by weight water andhaving a total solids content of 45.5% by weight, viscosity of about 400cps, average particle size of about 0.35 microns, and a glass transitiontemperature, midpoint, of about 17° C.).

Styrene butadiene latexes include, but are not limited to, UCAR™ LatexDL313 (a styrene butadiene latex comprising 48% by weight of acarboxylated styrene butadiene polymer and 52% by weight water having atotal solids content of 48% by weight, viscosity of about 300 cps,average particle size of about 0.1 microns, and a glass transitiontemperature, midpoint, of about −1° C.).

Vinyl acrylic latexes include, but are not limited to, UCAR™ Latex 162(a vinyl acrylic copolymer latex binder comprising about 55% by weightvinyl acetate, butyl acrylate polymer (CAS # 25067-01-0), 45% by weightwater, less than 0.1% by weight vinyl acetate, 0.04% by weightacetaldehyde, 0.01% by weight formaldehyde and having a total solidscontent of 55% by weight, viscosity of about 400 cps, average particlesize of about 0.3 microns, and a glass transition temperature, midpoint,of about 12° C.) and UCAR™ Latex 357 (a vinyl acrylic copolymer latexbinder comprising about 56% by weight vinyl acetate, butyl acrylatepolymer (CAS # 25067-01-0), 44% by weight water, less than 0.08% byweight vinyl acetate, 0.04% by weight acetaldehyde, 0.01% by weightammonia and having a total solids content of 56.5% by weight, viscosityof about 400 cps, average particle size of about 0.3 microns, and aglass transition temperature, midpoint, of about 23° C.).

Particular mention may be made of UCAR™ Latex 9042. The adhesiveproperties of UCAR™ Latex 9042 are characterized by: a 180° Peel,30-minute dwell, pli of 3.5, a Quick Stick Adhesion, pli of 1.5, andShear Resistance, on stainless steel, hours (½″×½″×500 g) of 9.0, astested on 2-mil polyester backing at a coat weight of 1.6-1.8 g/100 in²,73° F.

The compositions of the invention comprise an inorganic fire-retardant.In the broadest aspects of the invention, any inorganic fire-retardantmay be employed. Such inorganic fire-retardants are well-known in theart and include, without limitation, certain phosphate salts such asammonium polyphosphate, (NH₄PO₃)_(n), metal oxides, borates, and thelike. In one implementation of the invention, the inorganicfire-retardant is one which undergoes an endothermic reaction in thepresence of heat or flame (an “endothermic inorganic fire-retardant”).Crystalline materials having water of hydration are one interestingexample of endothermic inorganic fire-retardants. Suitable inorganicmaterials comprising water of hydration include, for example,crystalline oxides such as alumina trihydrate, hydrated magnesium oxide,and hydrated zinc borate, including but not limited to 2ZnO.3B₂O₃.3½H₂O,4ZnO.B₂O₃.H₂O, 4ZnO.6B₂O₃.7H₂O, and 2ZnO.2B₂O₃.3H₂O. Special mention maybe made of alumina trihydrate. It will be understood that the term“oxide,” as used herein, refers to inorganic substances comprising atleast one atom which forms at least one double bond to oxygen, andincludes substances having one atom double bonded to oxygen, for exampleMgO, and substances having two or more atoms double bonded to oxygen,for example zinc borate. The term “hydrated” refers to any substancewhich includes water in the crystalline state, i.e., water ofcrystallization, and is used synonymously herein with the term “water ofhydration.”

It has been observed that when particulate inorganic fire-retardantswhich are water-insoluble or poorly water-soluble having relativelylarge particle diameters (e.g., >20 microns) are formulated into anaqueous coating system, there is a tendency for the particulateinorganic fire-retardants to separate from the aqueous phase uponlengthy periods of storage. When this occurs, the sediment must bere-suspended, often with great difficulty, before applying the coatingsystem to a substrate. This undesirable characteristic is overcome byemploying particulate inorganic fire-retardant particles having arelatively small median particle diameter (e.g., <20 microns), alone orin combination with larger diameter particles of the inorganicfire-retardant. In particular, it has been found that very smallparticles, on the order of about 0.1 to about 5 microns, remainsuspended in aqueous solution for extended periods of time, at leastseveral days and preferably several weeks or more, without appreciablesedimentation. Coating systems formulated with such small particlediameter inorganic fire-retardants may therefore be employed without theneed for laborious shaking, stirring, etc.

Accordingly, one embodiment of the invention provides compositionscomprising inorganic fire-retardant powders having a median particlediameter of about 0.1 to about 5 microns. Within this range, inorganicfire-retardant powders having a median particle diameter of about 1 toabout 3 microns are contemplated to by especially useful. Particularmention may be made of inorganic fire-retardant powders having a medianparticle diameter of about 2 microns. It is within the skill in the artto provide such powders having various particle sizes between 0.1 and100 microns by disc milling, air-jet milling, grinding, and the like.These small diameter powders can be added to aqueous solutions inrelatively large quantities (e.g., >30% by weight) as compared to largerdiameter powders. The fire-retarding and fire-extinguishing benefits ofthe coating system are most fully realized when high levels of inorganicfire-retardant are present, particularly levels greater than 30% byweight of the total aqueous composition.

While the foregoing embodiments are contemplated to be useful forformulating many interesting coating systems of the invention, furtherimprovement in the fire-retardant and fire-extinguishing characteristicsof the coatings are achieved by employing a bimodal distribution ofparticulate inorganic fire-retardant. In one embodiment according tothis aspect of the invention, compositions are provided comprising afirst inorganic fire-retardant powder having a first median particlediameter and a second inorganic fire-retardant powder having a secondmedian particle diameter. The first median particle diameter is selectedsuch that the inorganic fire-retardant powder is capable of forming acolloidal suspension in aqueous solution which does not readilyprecipitate from the aqueous phase. The first median particle diameteris typically, although not necessarily, be between about 0.1 microns andabout 20 micron, although typically it will be between about 0.1 toabout 10 microns, or about 0.1 to about 5 microns, and suitably betweenabout 1 to about 3 microns. Inorganic fire-retardant powders having amedian particle diameter of about 2 microns have been found to beparticularly interesting when employed as the first inorganicfire-retardant powder. The second inorganic fire-retardant powder is arelatively larger powder than the first inorganic fire-retardant powder.It has been observed that larger powders provide a more substantialbarrier against heat and fire. Thus, the presence of larger particlesprovides a more robust coating and imparts a longer duration ofprotection to the coating. However, the diameter of the second powdershould not be so large such that the material readily forms a sedimentwhen formulated in an aqueous coating system. There is substantialleeway in the selection of the second powder because, in the broadestaspects of the invention, it is an optional expedient. The skilledartisan will be guided by the foregoing principles when selecting apreferred second particle diameter. The second median particle diameteris typically, though not necessarily, between about 5 microns and about100 microns. In one embodiment the second median particle diameter isbetween about 10 microns and about 70 microns. In another embodiment thesecond median particle diameter is between about 20 microns and about 60microns. Particularly useful coatings comprise a second inorganicfire-retardant powder having a median particle diameter between about 40and about 50 microns, such as, for example, about 45 microns.

It has surprisingly been found that the larger second inorganicfire-retardant powders will remain suspended in an aqueous solution whenthe smaller inorganic fire-retardant powders are also present. It iscontemplated that sedimentation of the larger second powder will beretarded or substantially prevented across a broad range of relativeproportions between the two powders. For example, the weight ratio ofthe first inorganic fire-retardant powder to the second inorganicfire-retardant powder will typically, though not necessarily, be about100:1 to about 1:20. The fire-retardant and fire-extinguishingproperties of the compositions will be enhanced when the weight ratio ofthe first inorganic fire-retardant powder to the second inorganicfire-retardant powder is about 5:1 to about 1:20. Other embodiments willcomprise a weight ratio of about 10:1 to about 1:10, about 5:1 to about1:5, and about 1:1 to about 1:5. A weight ratio of 1:3 has been found tobe particularly useful.

One interesting embodiment of the invention comprises a first inorganicfire-retardant powder having a median particle size of about 1 to about3 microns, and particularly about 2 microns, and a second inorganicfire-retardant having a median particle size of about 40 to about 50microns, and particularly about 45 microns.

In another interesting embodiment of the invention, trimodaldistributions of particulate inorganic fire-retardants are employed. Thecompositions according to this embodiment will comprise a firstinorganic fire-retardant powder having a first median particle diameter,a second inorganic fire-retardant powder having a second median particlediameter, and a third inorganic fire-retardant powder having a thirdmedian particle diameter. The first and third inorganic fire-retardantpowders are selected as described above for the bimodal compositions.The second inorganic fire-retardant powder is provided having a medianparticle size intermediate between the first and third median particlediameters. The second inorganic fire-retardant powder will typically,though not necessarily, have a median particle size between about 5microns and about 20 microns. Within this range, second inorganicfire-retardant powders having a median particle diameter between about 5and about 15 microns are contemplated to be useful. In one embodimentcontemplated to be useful, the second inorganic fire-retardant powderhas a median particle size of about 9 microns.

In one implementation of the invention the inorganic fire-retardantpowder is alumina trihydrate. The commercially available 2 micronalumina trihydrate powder MICRAL® 932 (J. M. Huber Corp.) has been founduseful as the first powder in the bimodal and trimodal embodimentsdescribed above. MICRAL® 932 is a high surface area ultrafine aluminatrihydrate having a typical chemical analysis of Al₂O₃ (64.9%), SiO₂(0.005%), Fe₂O₃ (0.007%), total Na₂O (0.3%), soluble Na₂O (0.12%), 34.6%loss on ignition (550° C.), and 0.8% free moisture (105° C.). MICRAL®932 is characterized by a median particle diameter of 2 microns, 100%passage through a 325 mesh sieve, and a surface area of 13 m²/gm asmeasured with a Quantachrome monosorb surface area analyzer. The secondalumina trihydrate powder (in bimodal embodiments) and the third aluminatrihydrate powder (in trimodal embodiments) suitably have a medianparticle size of about 45 microns. Alumina trihydrate powder having amedian diameter of about 45 microns is commercially available under thename Onyx Elite® 100 (J.M. Huber Corp.). Onyx Elite® 100 is an aluminatrihydrate having a typical chemical analysis of Al₂O₃ (65%), SiO₂(0.008%), Fe₂O₃ (0.004%), total Na₂O (0.2%), soluble Na₂O (0.015%),34.6% loss on ignition (550° C.), and 0.1% free moisture (105° C.). Thisalumina trihydrate powder is characterized by a median particle diameterof 45 microns, a surface area of 0.75 m²/gm as measured as measured witha Quantachrome monosorb surface area analyzer, and the following screenanalysis: 0-10% on 100 mesh, 65% on 200 mesh, 90% on 325 mesh, 10%through 325 mesh, and 5% less than 10 microns. In trimodalimplementations, a suitable alumina hydrate powder having a medianparticle size of 9 microns is commercially available under the nameHymod® SB432 CM (J.M. Huber Corp.). Hymod® SB432 CM has a typicalchemical analysis of Al₂O₃ (64.9%), SiO₂ (0.008%), Fe₂O₃ (0.007%), totalNa₂O (0.2%), soluble Na₂O (0.03%), 34.6% loss on ignition (550° C.), and0.23% free moisture (105° C.). This material is characterized by amedian particle diameter of 9.1 microns, a surface area of 2.15 m²/gm asmeasured with a Quantachrome monosorb surface area analyzer and a screenanalysis of 0.28% on 325 mesh and 99.7% through 325 mesh. In oneimplementation of the trimodal embodiment according to the invention,the composition comprises a first alumina hydrate powder having a medianparticle size of about 2 microns, a second alumina hydrate powder havinga median particle size of about 9 microns, and a third alumina hydratepowder having a median particle size of about 45 microns.

In addition to the bimodal and trimodal embodiments described above, itis contemplated that any number of powders having different medianparticle sizes may be employed in the practice of the invention.Accordingly, the invention embraces embodiments having one, two, threeor more inorganic fire-retardant powders (e.g. alumina hydrate powders)of differing median particle diameters. In one embodiment, the first andsecond (or first, second and third) powders are powders of the sameinorganic fire-retardant. However, the invention is not so limited ancontemplates embodiments where the first and second (or first, secondand third) powders are powders independently selected from differentinorganic fire-retardants.

Other alumina trihydrate powders having median diameters between about 1and about 100 microns are commercially available, for example, from theJ.M Huber Corporation under the names Hymod®, Onyx Elite® 100, andMICRAL®. With due regard to these commercially available aluminatrihydrate powders, it is contemplated that inorganic fire-retardantpowders having median particle diameters of, for example, about 1, 1.25,1.5, 2, 2.6, 3.5, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14.5, 15.5, 16, 18,18.5, 20, 25, 35, 40, 45, 50, 60, and about 70 will be useful in thepractice of the invention.

The compositions of the invention may contain any amount of inorganicfire-retardant. However, it has been found advantageous to includeinorganic fire-retardants in the inventive compositions at levels of atleast 30% by weight or greater to provide the most desirablefire-retardant and fire-extinguishing properties. It has surprisinglybeen found that relatively large diameter inorganic fire-retardantpowders will remain suspended in aqueous solution in the bi- andtri-modal compositions at levels which would otherwise rapidlyprecipitate from the aqueous phase and form an undesirable sediment inthe absence of smaller diameter powders.

It has been found to be advantageous, but not strictly necessary, toemploy a surfactant in the compositions of the invention. The use of asurfactant will allow for even larger amounts of inorganicfire-retardant to be incorporated in the compositions. This expedientwill be particularly advantageous where it is desired to employ onlylarge diameter inorganic fire-retardant powders in the inventivecompositions. With the use of a surfactant, it is possible toincorporate 30% by weight or more of inorganic fire-retardant powdershaving median diameters between about 10 and about 100 microns, whichwould otherwise readily separate from aqueous solution to form anundesirable sediment, even in the absence of smaller diameter particles.Any surfactant may be employed in the practice of the invention. Thesurfactant may be an anionic surfactant, including, for example, sodiumdodecylbenzene sulfate and sodium dodecylbenzene sulfonate or thesurfactant may be a nonionic surfactant, such as an alkyl arylpolyethoxy alcohol or an alkyl phenoxy poly(ethyleneoxy)ethanol havingalkyl groups of about 7 to about 12 carbon atoms, and the like.Combinations of one or more surfactants are also contemplated to beuseful in the practice of the invention. The nonionic octyl phenolethoxylate surfactant sold under the name TRITON®-X 100 (Rohm & Haas)has been found especially useful. The surfactant will typically bepresent at about 0.1 to about 5% by weight based on the total weightwater (i.e., aqueous latex dispersion plus added water). When asurfactant is present, it is not strictly necessary to employ bimodal ortrimodal inorganic fire-retardant powders.

The compositions of the invention typically will comprise at least about30% by weight inorganic fire-retardant. In other interestingembodiments, the compositions will comprise at least about 40% byweight, at least about 50% by weight, at least about 60% by weight, orat least about 70% by weight inorganic fire-retardant. For maximum fireprotection it may be desirable to include inorganic fire-retardants inthe compositions at least about 80% by weight or at least about 90% byweight.

In a particularly interesting embodiment of the invention, thecompositions are provided as water-resistant, fire-retardant,smoke-suppressing coatings for application to flammable substrates. Thecoatings are provided as aqueous dispersions having the compositions ofthe invention dispersed substantially homogenously therein. Accordingly,laborious stirring or agitation of the liquid to re-disperse theinorganic fire-retardant is not required. The liquid coating may bepackaged in cans and the like and applied to the substrate by, forexample, brushing or spraying.

In some embodiments, the coatings pass the “Surface BurningCharacteristics of Building Materials” standard ASTM E84-04 (UL E84)with a flame spread index of 0 and a smoke index of 0. The coatings alsopass Fed. Std. 141B, Method 6221 for flexibility with no cracking orchecking when bent 180° around a ⅛″ mandrel.

The coatings may be applied to any number of substrates including,without limitation, plastic, rubber, metal, composite materials, wood,synthetic fibers, and cellulosics such as, for example cardboard. Theadvantages of the invention are most fully realized when the substrateis deformable, i.e., flexible, pliable, ductile, etc. Exemplarysubstrates therefore include, without limitation: pipes; tubes; cables;cords; ropes; wires; hoses; weld blankets; automotive parts includingfor example; shifter boots, “soft tops,” fire walls, interior paneling,etc.; flexible panels; mats; molded plastic articles and the like. Ofcourse, the coatings will be equally useful when applied to rigidsubstrates.

The coatings may be applied over one or more under-coatings, includingfor example, intumescent coatings. Accordingly, one embodiment of theinvention provides a fire extinguishing system comprising a coatingaccording to the invention applied over one or more under-coatings,wherein at least one coating of the one or more under-coatings comprisesan intumescent composition. Suitable intumescent compositions andcoatings are well known in the art and include, for example, thosedisclosed in U.S. Pat. No. 5,035,951 to Dimanshteyn.

In other applications, the coatings are contemplated to be particularlysuitable for application to substrates which are subjected to water fromcondensation, outdoor use, high humidity environments, etc., including,for example, various HVAC components.

In another embodiment of the invention, the compositions are provided inthe form a paint, more particularly a latex paint, by incorporating oneor more pigments, including for example TiO₂, into the formulationsdescribed herein. Additional additives well known to the skilled artisansuch as pigment-dispersing agents, preservatives, thickeners, defoamers,and freeze-thaw stabilizers may also be included. The paints areadvantageously water-resistant and fire-resistant.

EXAMPLE 1

This example provides a bimodal coating according to the invention. Ahighly flexible water-resistant, fire-retardant, fire-extinguishingcoating is formulated according to Table 1.

TABLE 1 UCAR ™ Latex 9042 85 lbs water 27 lbs TRITON ®-X 100  2 lbs OnyxElite ® 100 (45 μm) 150 lbs  MICRAL ® 932 (2 μm) 50 lbs

EXAMPLE 2

A cement board was coated with a 15 mil thick coating according toExample 1 and subjected to surface burning testing according to the“Surface Burning Characteristics of Building Materials” standard ASTME84-04 (UL E84). See ASTM Fire Standards, Sixth Edition, ASTMInternational, Oct. 1, 2004 and Annual Book of ASTM Standards, Volume04.07, November 2004, the contents of which are hereby incorporated byreference in their entirety.

ASTM E84-04 compares surface flame spread and smoke developmentmeasurements to those obtained from tests of mineral fiber cement boardand select grade red oak flooring standards. The sample is subjected toflame for ten minutes while flame front advance and smoke densitymeasurements are recorded. No ignition of the coated surface wasobserved during the 10 minute exposure to flame reaching a maximumtemperature of 569.3° F. The results of the test are summarized in Table2.

TABLE 2 Parameter Index Max Flame Spread (ft) 0.0 Flame Spread Index 0Smoke Index 0

Based on the foregoing test, the coating is considered a “Class A”building material per UL E84.

EXAMPLE 3

The ability of the coating of Example 1 to resist fire was investigatedusing a non-asbestos weld blanket substrate. In the absence of thecoating, the weld-blanket ignited and evolved large amounts of smokeupon contact with molten metal from a welding torch. A coating accordingto Example 1 was applied to the same weld blanket. Molten metal wasdropped onto the coated weld blanket. No visible ignition or smoking wasobserved.

EXAMPLE 4

This example provides a trimodal coating composition according to theinvention. A highly flexible water-resistant, fire-retardant,fire-extinguishing coating is formulated according to Table 3.

TABLE 3 UCAR ™ Latex 9042 80 lbs water 30 lbs TRITON ®-X 100 3 lbs OnyxElite ® 100 (45 μm) 120 lbs Hymod ® SB432 CM (9 μm) 40 MICRAL ® 932 (2μm) 20 lbs

It will be understood that the recitation of ranges contained herein areas a matter of convenience only and the inventors are in possession ofevery value intermediate within the ranges. That is, every intermediatevalue or sub-range within a disclosed range should be understood to beinherently disclosed.

It should thus be understood that this description (including thetables) is only representative of some illustrative example variants.For the convenience of the reader, the above description has focused ona representative sample of all possible permutations and combinations, asample that teaches the principles of the invention. The description hasnot attempted to exhaustively enumerate all possible variations,permutations or combinations. That all such variants, permutations orcombinations have not been presented or may be available is not to beconsidered a disclaimer of those variants, permutations or combinations.One of ordinary skill will appreciate that many of those variants,permutations or combinations incorporate the very same principles andcan be achieved without undue effort, although in some cases they areliterally described herein and in other cases, although not specificallydescribed, are equivalent.

1. A fire-retardant composition comprising: (a) a latex binder; (b) atleast 40% by weight of alumina trihydrate having at least a bimodaldistribution of particle sizes comprising: (i) a first powder of aluminatrihydrate having a first median particle diameter between about 0.1 andabout 20 microns, and (ii) a second powder of alumina trihydrate havinga second median particle diameter between about 5 and about 100 microns;wherein said second median particle diameter is larger than said firstmedian particle diameter; and (c) a surfactant.
 2. The composition ofclaim 1 wherein said first powder has a median particle diameter betweenabout 1 and about 3 microns.
 3. The composition of claim 2 wherein saidfirst powder has a median particle diameter of about 2 microns.
 4. Thecomposition of claim 1 wherein said second powder has a median particlediameter between about 10 and about 70 microns.
 5. The composition ofclaim 4 wherein said second powder has a median particle diameterbetween about 20 and about 60 microns.
 6. The composition of claim 5wherein said second powder has a median particle diameter of about 40and about 50 microns.
 7. A coating consisting essentially of thecomposition of claim
 1. 8. A fire-retardant, smoke-suppressing coatingconsisting essentially of the composition of claim
 1. 9. Afire-extinguishing coating consisting essentially of the composition ofclaim
 1. 10. A water-resistant coating consisting essentially of thecomposition of claim
 1. 11. An adhesive consisting essentially of thecomposition of claim
 1. 12. A flexible barrier consisting essentially ofthe composition of claim
 1. 13. The composition of claim 1, wherein thelatex binder is selected from the group consisting of a natural latexpolymer; a neoprene latex polymer; a nitrile latex polymer; a vinylacrylic latex polymer; a styrene acrylic latex polymer; a styrenebutadiene latex polymer; a copolymer of methylmethacrylate, styrene,methacrylic acid, and 2-hydroxyethyl acrylate; a copolymer of acrylicacid, methyl methacrylate, styrene, hydroxyethyl acrylate, andbutylacrylate; a copolymer of butylacrylate, methyl methacrylate, andhydroxyethyl acrylate; a copolymer of styrene and butylacrylate; acopolymer of butylacrylate, 2-ethylhexyl acrylate, and methacrylic acid;carboxylated styrene butadiene polymers; a copolymer of butyl acrylate,2-ethylhexyl acrylate, methyl methacrylate, and acrylic acid; acopolymer of butyl acrylate, methyl methacrylate, styrene, methacrylicacid, and 2-hydroxyethyl acrylate; and a copolymer of vinyl acetate andbutyl acrylate.
 14. The composition of claim 1, wherein the compositioncomprises water.